Mass distribution in our Galaxy

This article summarizes recent work on the luminosity and mass distribution of the galactic bulge and disk, and on the mass of the Milky Way's dark halo. A new luminosity model consistent with the COBE NIR data and the apparent magnitude distributions of bulge clump giant stars has bulge/bar length of similar or equal to 3.5 kpc, axis ratios of 1:(0.3-0.4):0.3, and short disk scale-length (similar or equal to 2.1 kpc). Gas-dynamical flows in the potential of this model with constant M/L fit the terminal velocities in 10degrees less than or equal to \l\ less than or equal to 50degrees very well. The luminous mass distribution with this M/L is consistent with the surface density of known matter near the Sun, but still underpredicts the microlensing optical depth towards the bulge. Together, these facts argue strongly for a massive, near-maximal disk in our similar to L-*, Sbc spiral galaxy. While the outer rotation curve and global mass distribution are not as readily measured as in similar spiral galaxies, the dark halo mass estimated from satellite velocities is consistent with a flat rotation curve continuing on from the luminous mass distribution.